diff --git a/lib/Controller/WopiController.php b/lib/Controller/WopiController.php
index 1b56319be8..8d608a4bb8 100644
--- a/lib/Controller/WopiController.php
+++ b/lib/Controller/WopiController.php
@@ -273,9 +273,12 @@ public function checkFileInfo($fileId, $access_token) {
 			$response['UserExtraInfo']['avatar'] = $this->urlGenerator->linkToRouteAbsolute('core.avatar.getAvatar', ['userId' => $wopi->getEditorUid(), 'size' => self::WOPI_AVATAR_SIZE]);
 			if ($this->groupManager->isAdmin($wopi->getEditorUid())) {
 				$response['UserExtraInfo']['is_admin'] = true;
+			} else {
+				$response['UserExtraInfo']['is_admin'] = false;
 			}
 		} else {
 			$response['UserExtraInfo']['avatar'] = $this->urlGenerator->linkToRouteAbsolute('core.GuestAvatar.getAvatar', ['guestName' => urlencode($wopi->getGuestDisplayname()), 'size' => self::WOPI_AVATAR_SIZE]);
+			$response['UserExtraInfo']['is_admin'] = false;
 		}
 
 		if ($isPublic) {